The Swedish printed application No. 7902979-9 discloses a method of absorbing vapor from a gas, whereby the gas is subjected in a counter flow to an adiabatic absorption effect by a liquid which, as the only volatile component, includes the material which condenses in the absorption and also other non-volatile components having the characteristic, at high concentrations, of substantially reducing the vapor pressure of the volatile material over the liquid. If the absorption liquid is an aqueous solution, then, for example, potassium acetate, sodium acetate, potassium carbonate, calcium chloride, lithium chloride or lithium bromide can be used.
A disadvantage of the described absorption method is that the concentration of the absorption liquid decreases because it is continuously diluted due to the vapor absorption, resulting in an increase of the vapor pressure of the volatile component over the liquid. When the concentration of the salt solution has decreased to a certain level at which the equilibrium prevails between the partial pressure of the vapor in the gas and the partial pressure of the liquid over the solution, the vapor absorption will stop. To a certain extent this can be advantageously affected by using large amounts of absorption liquid or a large number of absorption stages, but it has a negative effect on the heat and the total economy of the system. In order to avoid said negative effect the gas is dehumidified to such humidity content as to be in equilibrium with the diluted absorption liquid.